1. Field of the Invention
The present invention relates to novel thermotropic semialiphatic copolyesteramides comprising recurring structural units emanating from an aromatic dicarboxylic acid or derivative thereof, from a diphenol or derivative thereof, and from an aliphatic amino acid and/or a lactam and/or a diacidic polyamide or derivatives thereof, as well as to a process for the preparation of such novel thermotropic copolyesteramides.
The amide copolyesters of the present invention are thermotropic, namely, they can be converted into anisotropic melts which are easy to shape by spinning or molding.
2. Description of the Prior Art
As indicated in EP-A-0,010,051, a demonstration of the anisotropy of polyesters can be carried out using the TOT thermooptical method described in FR-A-2,270,282. When the copolymer is observed in the molten state in optical systems equipped with crossed polarizers, transmission of polarized light and creation of a strong birefringence are produced, whereas the light transmission and the birefringence are nil in the case of isotropic materials. As a result of these phenomena, anisotropic melts have a specific orientation and a relatively high degree of organization which are transferred to articles shaped therefrom, such as filaments, films and molded objects, providing them, even in the raw state, with such improved properties as modulus and tenacity which typically are not encountered in isotropic raw materials. In particular, these molded shaped articles have advantageous characteristics and properties in one direction, which are comparable to those of plastics reinforced with glass fibers.
The thermotropic copolyesteramides described in EP-A-0,010,051, and also in EP-A-0,007,715, U.S. Pat. Nos. 4,330,457, 4,355,132 and 4,182,842, and FR-A-2,607,818 essentially consist of wholly aromatic and/or cyclic recurring structural units.
In general, while the thermotropic copolymers exhibit excellent mechanical properties, they have, on the other hand, high melting temperatures: on the order of 200.degree. to 400.degree. C. and more typically from 270.degree. to 370.degree. C. These high temperatures require specialized conversion apparatus and present energy requirements which are higher than those needed to convert conventional resins. Furthermore, when the melt temperatures are high, molded shaped articles that have excellent mechanical properties are difficult, if not impossible to produce.